从 Java 中的 Curl Post 请求获取 Json / 响应正文

Question

这是我编写的发送 POST 请求发送电子邮件的方法。我能够发送电子邮件并获得响应代码 200 Ok。但我不知道如何获取 JSON 响应并将其转换为对象。有人可以告诉我该怎么做吗？

public void sendEmail() {
        try {
            URL url = new URL("https://mandrillapp.com/api/1.0/messages/send");

            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setRequestProperty("Content-Type", "application/json");

            String data =
                    "{\"key\": \"" + mailchimpApiKey + "\", " +
                            "\"message\": {" +
                            "\"from_email\": \"from@gmail.com\", " +
                            "\"subject\": \"Hello World\", " +
                            "\"text\": \"Welcome to Mailchimp Transactional!\", " +
                            "\"to\": [{ \"email\": \"to@gmail.com\", \"type\": \"to\" }]}}";

            byte[] out = data.getBytes(StandardCharsets.UTF_8);

            OutputStream stream = httpURLConnection.getOutputStream();
            stream.write(out);

            System.out.println(httpURLConnection.getResponseCode() + " " + httpURLConnection.getResponseMessage());

            httpURLConnection.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Answer 1

基本搜索显示：https://www.baeldung.com/httpurlconnection-post#8-read-the-response-from-input-stream

try(BufferedReader br = new BufferedReader(
  new InputStreamReader(con.getInputStream(), "utf-8"))) {
    StringBuilder response = new StringBuilder();
    String responseLine = null;
    while ((responseLine = br.readLine()) != null) {
        response.append(responseLine.trim());
    }
    System.out.println(response.toString());
}

如果响应采用 JSON 格式，请使用任何 third-party JSON 解析器，例如 Jackson 库、Gson 或 org.json 来解析响应。

Answer 2

您可以根据收到的 response code 得到 errorStream 或 inputStream 并从中得到响应。下面的示例从流

创建一个 BufferedReader

BufferedReader br = null;
if (100 <= httpURLConnection.getResponseCode() && httpURLConnection.getResponseCode() <= 399) {
    br = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream()));
} else {
    br = new BufferedReader(new InputStreamReader(httpURLConnection.getErrorStream()));
}

然后您可以根据需要从 br 中读取和存储数据。下面将数据存入StringBuilder

StringBuilder data = new StringBuilder();
    String dataLine = null;
    while ((dataLine = br.readLine()) != null) {
        data.append(dataLine.trim());
    }
    System.out.println(data.toString());

除了打印为 String，您还可以使用 JSON 库将其转换为 JSON。您可以关注 this guide

Answer 3

除了@mdre的回答

我使用 org.json 库将响应转换为 JSON 对象。以下方法正是这样做的：

import org.json.JSONException;
import org.json.JSONObject;

    public static JSONObject convertResponseToJSONObject(String responseString) {
        try {
            JSONObject jsonObj = new JSONObject(responseString);
            return jsonObj;
        } catch (JSONException e) {
            System.err.println(
                "It is not possible to create a JSONObject from the input string, returning null. Exception:");
            e.printStackTrace();
        }
        return null;
    }

请注意，如果响应以 { 开头，则响应仅表示 JSON 对象。如果它以 [ 开头，则响应表示一个 JSON 数组。

从 Java 中的 Curl Post 请求获取 Json / 响应正文

Get Json / Resonse body from Curl Post Request in Java

java

json

curl